Manufacture of tetraalkyllead



a I catalyst, chemical equation:

Patented Dec. 26, 1950 MANUFACTURE OF TETRAALKYLLEAD il'yniin Shapiro, Detroit, Mich., assignor to Ethyl Corporation, New York, N. Y., a corporation of Delaware No Drawing. Application May 29, 1948, Serial No. 30,191

6 Claims.

This invention relates to a catalytic process for the manufacture of tetraalkyllead from magnesium-lead alloy and certain of the alkyl halides. More particularly, it relates to a process for reacting a magnesium-lead alloy with an alkyl halide selected from the group consisting of chlorides, bromides, iodides in the presence of selected catalysts to form a tetraalkyllead.

The manufacture of tetraethyllead is of considerable importance because of its use as an antiknocl: agent in motor fuels. It is used in most of the gasolines presently marketed. Therefore, the economics of its manufacture is also of major importance.

The present commercial process for the manufacture of tetraethyllead has been used for a number of years, and, in general, is satisfactory. However, it has certain disadvantages which are overcome by practicing my invention. The present commercial process is expressed by the following chemical equation:

originally present in the alloy is converted to tetra'ethyllead. The remaining three-quarters of the original lead present is converted tofinely" divided metal considerably contaminated with the product. The presence of this large amount of unused lead in the autoclaves makes temperature control difficult, results in a low overall rate of product output, and necessitates a relatively large investment in equipment as compared with the more efiicient processing of lead obtainable in practicing my invention. Furthermore, the conversion of the finely divided lead to a form suitable for use in making the NaBb alloy is a hazardous and expensive operation.

It is an object of this invention to provide a process for making tetraalkyllead overcoming the above objections, particularly in making more efficient use of the lead. This is accomplished in my invention by reacting certain alkyl halides with magnesium-lead alloy in the presence of as illustrated by the following Temp. MgiPb 102E501 Tr (CgH)4Pb 2Mg0lz It is to be noted that in the above equation, .no lead in the alloy is converted to metallic lead as contrasted with over '75 per cent lead converted from the alloy to finely divided metal in the present commercial operations? 25 methyl diphenyl amine.

2 The above reaction is carried out in the presence of catalysts. While neither the exact mechanism of the reaction nor the effect of catalyst structure on the reaction is known, I have found 5 that organic carbon compounds containing an atom capable of chemical coordination with a magnesium-containing compound arethe most effective. Among the catalysts having such properties are aliphatic ethers, tertiary amines including aliphatic and aromatic tertiary amines,

and hydrocarbon-substituted ammonium iodides, including aliphaticand aromatic-substituted ammonium iodides. In all the compounds coming within the above groups, the coordinating atom is either oxygen or nitrogen.

matic amines or mixtures thereof produce good results. Examples of the amines are trialkyl amines, such as triethyl amine, tripropyl amine, tributyl amine, alkyl phenyl amines, such as dimethyi phenyl amine, diethyl phenyl amine, and Also, amines such as pyridine have been successfully used. High yields of tetraalkyllead compounds have been obtained using alkyl or aromatic ammonium iodides such as trimethylphenyl ammonium iodide, tetrabutyl ammonium iodide, and tetraethyl ammonium corresponding tetraalkylleadcompounds, such as the monochloro derivatives of methane, ethane, propane, butane, and pentane, as well as the corresponding bromides and iodides. For example, ethyl chloride, ethyl bromide, methyl bromide, isopropyl bromide, isobutyl bromide, and. n-butyl iodide have been successfully employed.

My process can be carried out at temperatures up to 150 C. although the preferred range is'80 responding to MgzPb (19.01 per cent Mg by weight), but good yields are obtainable with a magnesium content varying from 18 to 22 per cent by weight. As the magnesium content varies outside of this range inferior results are obtained, and furthermore, the alloy is more difficult to crush preparatory to using.

The time for the reaction can also be varied over a wide range. In closed bomb operations, the reaction time has been varied between two.

and sixteen hours with good results. The amount.

of catalyst can also be varied within wide limits, i. e., between 1 and per cent by'weight of the are ordinary commercial grades.

alloy charged has been used. The proportion of the particular catalyst used, and the operating conditions of temperature, pressure and time will vary with the alkyl halide used in order for optimum results to be obtained, and such variables need to be correlated to obtain high yields of tetraalkyllead compounds.

My invention is further illustrated by the following example: grams of MgzPb alloy, 20 grams of ethyl chloride and 5 grams of ethyl ether catalyst were introduced into a tumbled bomb. The alloy, comprising about 19 per cent by weight magnesium, was first ground in a chipmunk crusher to a particle size varying from four to 100 mesh, substantially three-quar- ,tcrs'of the ground alloy being in the range of four to 40-mesh. The ethyl chloride and the ether The materials are charged into the bomb preferably in the order: alloy, ethyl chloride, and ethyl ether. The bomb was then closed off and tumbled for six hours at 80 C. The reaction is exothermic and cooling is employed after the reaction is under way in order to maintain the desired temperature. In this experiment, the temperature was controlled by the controlling of the temperature of the bath in which the bomb was immersed. In commercial practice, cooling water suitably a pplied can be used. The pressure in this experiment reached a maximum of 80 pounds per square inch. At the endof six hours, the bomb was cooled and the product analyzed for tetra- ,ethyllead. Again, in commercial operations the product can bedistilled in vacuum or in the presence of steam to recover the tetraalkyllead product. In this example, an analysis showed that 6.07 grams of tetraethyllead were produced, which entitled Summary of Experiments. The results of twenty-three additional experiments conducted in a similar manner are also tabulated in the table. In all the examples, 10 grams of MgzPb alloy, comprising about 19 per cent by weight magnesium was used. The twenty-four examples illustrate results obtained with different alkyl halides added in varying amounts, different catalysts added in varying amounts, and different operating conditions with tetraalkyllead yield varying from 25 to 85 per cent by weight based on the lead input.

Referring to the table, Column 1 gives the example number; Columns 2, 3 and 4..refer to the alkyl halide; Column 2, the name, Column 3, the theories, and Column 4, the grams charged. The theories are the ratio of alkyl halide charged to the theoretical amount required for the lead to be completely reacted. Columns 5, 6, and '7 refer to the conditions of operation; Column 5, to the length of time the reactants remained in the bomb; Column 6, to the temperature maintained during reaction, and Column 7, to the pressure in pounds per square inch. The pressure in the experiments tabulated was not controlled, but was the pressure resulting from the materials charged at the temperature under which the bomb was maintained. Again referring to the table, Colis equivalent to per cent by weight, based on umns 8, 9, and 10 relate to the catalyst used, Column 8 to the name; Column 10 to the grams charged, and Column 9 the per cent by weight of catalyst based on alloy charged. Columns 11 and 12 relate to the tetraalkyl product; Column 11, to the grams recovered, and Column 12 to the percentage yield based on the lead in the alloy charged.

In Examples 1 to 20, inclusive, single catalysts were used. In runs 21 to 24, inclusive, double catalysts were used. It should be noted that, in general, the yield increased by using a double catalyst. The use of single or multiple catalysts depends principally on the alkyl halide charged I and the desired conditions of operation.

Summary of experiments Alkyl Halide Conditions Catalyst Yield 9 Pressure 1 0. Name 55 Grams 32E518, 3 61?" fil r Name 22 Grams Grams 23 1 Ethylflhlorldenfl; '2 20 6 80 80 Ethyl EtheL 5.0 6.07 48.0 2 "do-" 2 20 16 80 71 Dimethylphenyl amine 66 6. 6 6. 16 48. 7 5 50 2 120 207 Ethyl Ether 50 5. O 5. 61 44.4 5 50 2 120 198 Triethyl mine 5.5 6:25 49. 4 5 50 2 120 202 Dilncthylphenyl amine. .j 43. 5 4. 35 3. 21 25. 4 5 50 2 120 205 Pyridine 25. 0 2. 5 4.15 32. 9 5 50 2 120 201 Tetrablltylammonium iodide 133.0 13.3 6.35 50.2 5 50 120 202 Trilleshylphellyl ammonium 94. 0 9.4 3.87 30. 6

' 1o 1 e. '5 50 2 120 269 Dimethyl Ether i 50.0 5. O 3. 10 25.0 5 50 2 120 197 Di rl eth yl Ether of Ethylene 50.0 5.0 e 4.96 39.2

yco 5 50 2 120 202 DiOXPne 50. 0 v 5. O 4. 10 '32. 4 1 17 .16 100 Ethyl Ether 15.0 1. 5 -5. 66 44.8 2 34 4 100 70 .do .l 20.0 2.0 7. ll 50. 2 2 34 4 100 100 Methyl Ether 12. 4 l. 24 4. 49 35. 5 2 34 4 100 62 DiGniethwether ol' Ethylene 24. 4 2.44 4. 82 38. 1

' yco d0 2 34 16 100 02 D-HQXYI Ethel 50.0 5. 0 v 3.34 26.4 Methyl Bromide. 2 30 2 120 277 Ethyl Et 50 5- 0 6. 62 52.4 Isopropyl Bromide 1. 5 28.8 16 14 d 10 1.0 3. 34 26. 4 Isobutyl Bromide 1.-5 32.1 16 .80 6 10 l. 0 8. 44 27. 2 n-Butyl Iodide,, 1. 5 43.1 16 80 6 O 10. 76 85. l

- 5 Ethyl 2 34 4 70 {Dimethylphenylamine l 0.1 Ethyl Ghloride 2 20 s so as {lgg gggg ggg g :3 s. as 66.1

Ethyl Ether 10 1.0 23 2 20 6 80 83 {Eimelthylphenylammah I; 0.3 9

l y or 0.5 24 2 20 2 100 138 {Tetraethylammonium Iodide. 16.5 1.65.

invention comprise organiccompounds containing compound. Therefore, my catalyst is an organic, chemical coordination catalyst which is defined in the above terms.

In allcases, an excess of alkyl halide over the theoretical. amount required is preferred. Not only does; an excess increase the yield, but also it increases the rate of production which is important inilcommercial operation because it reduces equipment size and cost.) Also, an excess of halide maintains a liquid. which provides for betterheat transfer in maintaining by cooling, the desiredtemperature of operation.

The examples given herein are illustrative of my invention, but do not limit the scope of my invention; The reaction can be carried out in batch or in continuous operations. The manner of operation, as well as the equipment used can be varied considerably within the scope of my invention.

I claim:

1'. A process for making tetraalkyllead comprising alkylating lead in an alloy consisting of lead and magnesium in the preseuce of an alkylating catalyst containing an atom which chemieally coordinates with magnesium.

2. A process for making tetraalkyllead comprising reacting a lower alkyl halide with an alloy consistingot lead and magnesium in the presence of a catalyst selected from the group consisting of aliphatic hydrocarbyl ethers, tertiary hydrocarbyl amines and tetrahydrocarbyl ammonium iodides.

3. A process for making tetraalkyllead comprising reacting a lower alkyl halide with an alloy consisting of lead and magnesium in the presence of an aliphatic hydrocarbyl ether.

4. A process for making tetraethyllead comprising reacting an ethyl halide with an alloy consisting of about 18 to 22 per cent by weight magnesium and about 78 to 82 per cent by weight lead in the presence of a lower dialkyl ether.

5. A process for making tetraethyllead comprising reacting thyl chloride with an alloy consisting of about 18 to 22 per cent by weight magnesium and about 78 to 82 per cent by weight lead in the presence of diethyl ether.

6. A process for making tetraethyllead comprising reacting ethyl chloride with an alloy consisting of about 19 per cent by weight magnesium and about 81 per cent by weight lead in the presence of diethyl ether.

HYMIN SHAPIRO.

REFERENCES CITED Calingaert: Chemical Reviews, vol. 2 (1925), pp. 46-48.

Karrer: 712-714.

Number Organic Chemistry" (1938), PP. 

1. A PROCESS FOR MAKING TETRAALKYLLEAD COMPRISING ALKYLATING LEAD IN AN ALLOY CONSISTING OF LEAD AN DMAGNEXIUM IN THE PRESEUCE OF AN ALKYLATING CATALYST CONTAINING AN ATOM WHICH CHEMICALLY COORDINATES WITH MAGNESIUM. 